Kara A Livingston1, Jennifer B Rosen2, Jane R Zucker3, Christopher M Zimmerman2. 1. Centers for Disease Control/Council of State and Territorial Epidemiologists Applied Epidemiology Fellowship, Atlanta, GA, USA. Electronic address: kara.livingston@tufts.edu. 2. Bureau of Immunization, New York City Department of Health and Mental Hygiene, New York, NY, USA. 3. Bureau of Immunization, New York City Department of Health and Mental Hygiene, New York, NY, USA; Immunization Services Division/National Center for Immunization and Respiratory Diseases/Centers for Disease Control & Prevention, Atlanta, GA, USA.
Abstract
BACKGROUND AND OBJECTIVES: Mumps outbreaks have been reported among vaccinated populations, and declining mumps vaccine effectiveness (VE) has been suggested as one possible cause. During a large mumps outbreak in New York City, we assessed: (1) VE of measles-mumps-rubella vaccine (MMR) against mumps and (2) risk factors for acquiring mumps in households. METHODS: Cases of mumps were investigated using standard methods. Additional information on disease and vaccination status of household contacts was collected. Case households completed follow-up phone interviews 78-198 days after initial investigation to ascertain additional cases. Mumps cases meeting the study case definition were included in the analysis. Risk factors for mumps were assessed, and VE was calculated using secondary household attack rates. RESULTS: Three hundred and eleven households with 2176 residents were included in the analysis. The median age of residents was 13 years (range <1-85), and 462 (21.2%) residents met the study mumps case definition. Among 7-17 year olds, 89.7% received one or more doses of MMR vaccine, with 76.7% receiving two doses. Young adults aged 10-14 years (OR=2.4, CI=1.3-4.7) and 15-19 years (OR=2.5, CI=1.3-5.0) were at highest risk of mumps. The overall 2-dose VE for secondary contacts aged five and older was 86.3% (CI 63.3-94.9). CONCLUSIONS: The two-dose effectiveness of MMR vaccine against mumps was 86.3%, consistent with other published mumps VE estimates. Many factors likely contributed to this outbreak. Suboptimal MMR coverage in the affected population combined with VE may not have conferred adequate immunity to prevent transmission and may have contributed to this outbreak. Achieving high MMR coverage remains the best available strategy for prevention of mumps outbreaks.
BACKGROUND AND OBJECTIVES: Mumps outbreaks have been reported among vaccinated populations, and declining mumps vaccine effectiveness (VE) has been suggested as one possible cause. During a large mumps outbreak in New York City, we assessed: (1) VE of measles-mumps-rubella vaccine (MMR) against mumps and (2) risk factors for acquiring mumps in households. METHODS: Cases of mumps were investigated using standard methods. Additional information on disease and vaccination status of household contacts was collected. Case households completed follow-up phone interviews 78-198 days after initial investigation to ascertain additional cases. Mumps cases meeting the study case definition were included in the analysis. Risk factors for mumps were assessed, and VE was calculated using secondary household attack rates. RESULTS: Three hundred and eleven households with 2176 residents were included in the analysis. The median age of residents was 13 years (range <1-85), and 462 (21.2%) residents met the study mumps case definition. Among 7-17 year olds, 89.7% received one or more doses of MMR vaccine, with 76.7% receiving two doses. Young adults aged 10-14 years (OR=2.4, CI=1.3-4.7) and 15-19 years (OR=2.5, CI=1.3-5.0) were at highest risk of mumps. The overall 2-dose VE for secondary contacts aged five and older was 86.3% (CI 63.3-94.9). CONCLUSIONS: The two-dose effectiveness of MMR vaccine against mumps was 86.3%, consistent with other published mumps VE estimates. Many factors likely contributed to this outbreak. Suboptimal MMR coverage in the affected population combined with VE may not have conferred adequate immunity to prevent transmission and may have contributed to this outbreak. Achieving high MMR coverage remains the best available strategy for prevention of mumps outbreaks.